The New LS7

The most significant Corvette engine since the first small-block?

Once again, the big news from General Motors revolves around theCorvette, this time centering on the introduction of the race-derived427-cube LS7 powerplant that motivates the new '06 Z06. With a rated 500hp at 6,200 rpm and a 7,000 rpm redline, it's an engine that's sure toplease.

From an engine builder's perspective, looking at new OE engine designsalmost always leaves us with a trace of self satisfaction and maybe ahint of smugness. Looking over a newly introduced factory powerplant, wemay say, "That's a nice piece." Inside, however, the hot-rodder thatlives in our consciousness leaves us with a pleasant thought: Nice for astocker, but I can make it better.

Qualified that way, we feel an air ofhaughtiness, real or imagined, while reveling in what the OE left on thetable for us to exploit. Some porting in the heads, a little morecompression, trick rings and bore finishes, lightweight parts, and soon; our hot-rodder's bag of tricks runs deep. Unconstrained by theimpositions faced by mass production, our custom efforts allow us thefancy of outdoing monolithic corporations wielding unimaginableresources. Normally, this ego self-gratification is part and parcel ofany OE engine review. Then it happened: the LS7 small-block debut. Theonly reactions for someone truly in the know are deference and awe.

3/11

The fantastic cylinder heads define the engine and are key to its powerproduction. Reportedly achieving airflow in the realm of serious racepieces, the ports are substantially revised.

Thesize alone gives it credence: 427 cubic inches in its all-aluminumsplendor. Matching the displacement (coincidentally?) made famous by themost legendary of performance Corvettes from a generation long past,this is the largest "small-block" engine ever produced by GeneralMotors, while maintaining the external dimensions of previous Gen IVsmall-blocks. But it encompasses so much more than its internal girth.With a rated output of 500 SAE net horsepower at 6,200 rpm, the realmechanical energy emanating from this beast far outstrips any of thebig-blocks of yore.

Based on the groundbreaking Gen IV small-blockarchitecture introduced as the LS1 in 1997, the LS7 is much more thansimply a displacement increase. It's an exotic 7,000-rpm race-derivedpowerplant brought upon the public at a level of execution unrivaled inany production car. Dave Muscaro, assistant chief engineer for passengercar V-8s, put it succinctly, "In many ways, the LS7 is a racing enginein a street car. We've taken much of what we've learned over the yearsfrom the 7-liter C5-R racing program and instilled it here. The realityis, there has been nothing like it offered in a GM production vehicle."

MORE PHOTOS

VIEW FULL GALLERY

xclose

The New LS7

Once again, the big news from General Motors revolves around theCorvette, this time centering on the introduction of the race-derived427-cube LS7 powerplant that motivates the new '06 Z06. With a rated 500hp at 6,200 rpm and a 7,000 rpm redline, it's an engine that's sure toplease.

The fantastic cylinder heads define the engine and are key to its powerproduction. Reportedly achieving airflow in the realm of serious racepieces, the ports are substantially revised.

The intake ports are said to flow in the 360-cfm range at 28-inch waterdepression, and are fully CNC-ported. Ports feature a revised raisedentrance and a larger cross section to work with the larger displacementof the LS7.

Combustion chambers are likewise fully machined to this masterfullysculpted form and are stuffed with enormous 2.200-inch intake valves and1.61-inch exhaust valves. The valve angle in the cylinder heads relativeto the decks has been altered to 12 degrees for enhanced airflow, adeparture from the 15-degree angle employed by other Gen IVsmall-blocks. The chamber design offers significant quench area forefficient combustion.

The intake and exhaust valves are longer than the previous Gen IVvalves, providing room for deeper ports in the bowl area and over theport's critical short-side turn. The intake valve is titanium, while theexhaust features a hollow sodium-filled stem for enhanced heat transfer.

This paring of an intake and exhaust rocker illustrates the 9mm offsetemployed on the intake rocker (left). The offset alters the pushrodposition outward, providing increased port width in an area normallyconstricted. The lightweight rockers are highly refined for low mass andinertia, and feature needle-bearing pivots. The rocker ratio has beenincreased to 1.8:1, amplifying the motions directed by the camshaft.

The deep CNC-ported exhaust ports are said to deliver 214 cfm of airflow at 28-inch water depression. Also visible are the beehive-shapedvalvesprings, which reduce critical mass and are less prone to harmonicdisturbance than conventional parallel-wound springs. The small-diameterretainers also reduce mass at the valve side of the system.

Titanium is used as the connecting-rod material, an exotic find even inracing engines. Strength, light weight, and fatigue resistance make it aworthy upgrade in a large, high-rpm engine like the LS7.

The pistons feature a friction-reducing skirt coating and hard anodizedring lands, reducing wear and adding to reliability. The ring package islightweight and reactive for effective cylinder sealing well into theupper-rpm range.

Read all about the LS7 camshaft and power package installation we perform on this Chevy Corvette Z06. Only at www.gmhightechperformance.com, the official website for GM High-Tech Performance Magazine! » Read More